U.S. patent number 8,852,358 [Application Number 13/191,598] was granted by the patent office on 2014-10-07 for process for surface treating aluminum or aluminum alloy and article made with same.
This patent grant is currently assigned to Hon Hai Precision Industry Co., Ltd., Hong Fu Jin Precision Industry (ShenZhen) Co., Ltd.. The grantee listed for this patent is Hsin-Pei Chang, Cheng-Shi Chen, Wen-Rong Chen, Huann-Wu Chiang, Dun Mao. Invention is credited to Hsin-Pei Chang, Cheng-Shi Chen, Wen-Rong Chen, Huann-Wu Chiang, Dun Mao.
United States Patent |
8,852,358 |
Chang , et al. |
October 7, 2014 |
Process for surface treating aluminum or aluminum alloy and article
made with same
Abstract
A process for surface treating aluminum or aluminum alloy
comprises the following steps. Providing a substrate made of
aluminum or aluminum alloy. The substrate is treated with a
chemical conversion treatment solution containing molybdate as the
main film forming agent, to form a molybdate conversion film on the
substrate. Then, a ceramic coating comprising refractory compound
is formed on the molybdate conversion film by physical vapor
deposition.
Inventors: |
Chang; Hsin-Pei (New Taipei,
TW), Chen; Wen-Rong (New Taipei, TW),
Chiang; Huann-Wu (New Taipei, TW), Chen;
Cheng-Shi (New Taipei, TW), Mao; Dun (Shenzhen,
CN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Chang; Hsin-Pei
Chen; Wen-Rong
Chiang; Huann-Wu
Chen; Cheng-Shi
Mao; Dun |
New Taipei
New Taipei
New Taipei
New Taipei
Shenzhen |
N/A
N/A
N/A
N/A
N/A |
TW
TW
TW
TW
CN |
|
|
Assignee: |
Hong Fu Jin Precision Industry
(ShenZhen) Co., Ltd. (Shenzhen, CN)
Hon Hai Precision Industry Co., Ltd. (New Taipei,
TW)
|
Family
ID: |
46379682 |
Appl.
No.: |
13/191,598 |
Filed: |
July 27, 2011 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20120168034 A1 |
Jul 5, 2012 |
|
Foreign Application Priority Data
|
|
|
|
|
Dec 30, 2010 [CN] |
|
|
2010 1 0614785 |
|
Current U.S.
Class: |
148/275; 148/243;
148/240 |
Current CPC
Class: |
C23G
1/22 (20130101); C23C 22/78 (20130101); C23F
1/36 (20130101); C23C 28/34 (20130101); C23C
14/0676 (20130101); C23C 22/44 (20130101); C23C
28/345 (20130101); C23C 28/3455 (20130101); C23C
14/024 (20130101) |
Current International
Class: |
C23C
22/40 (20060101) |
Field of
Search: |
;148/240,243,275 |
Primary Examiner: Zheng; Lois
Attorney, Agent or Firm: Novak Druce Connolly Bove + Quigg
LLP
Claims
What is claimed is:
1. A process for surface treating aluminum or aluminum alloy, the
process comprising the following steps of: providing a substrate
made of aluminum or aluminum alloy; forming a molybdate conversion
film on the substrate by a chemical conversion treatment using a
chemical conversion treatment solution containing molybdate as the
main film forming agent; and forming a ceramic coating comprising a
refractory compound on the molybdate conversion film by physical
vapor deposition.
2. The process as claimed in claim 1, wherein the chemical
conversion treatment solution is an aqueous solution containing
about 8 g/L-15 g/L sodium molybdate Na.sub.2MoO.sub.4, about 1
g/L-3 g/L NaF, and about 6 g/L-10 g/L KMnO.sub.4; the pH value of
the chemical conversion treatment solution is in a range between
about 2 and 4.
3. The process as claimed in claim 2, wherein the chemical
conversion treatment is carried out by bringing the substrate in
contact with the chemical conversion treatment solution maintained
at a temperature of about 25.degree. C.-40.degree. C. for about 4
min-7 min.
4. The process as claimed in claim 2, wherein the chemical
conversion treatment solution is an aqueous solution containing
about 10 g/L Na.sub.2MoO.sub.4, about 1 g/L NaF, and about 8 g/L
KMnO.sub.4; the pH value of the chemical conversion treatment
solution is about 3.
5. The process as claimed in claim 4, wherein the chemical
conversion treatment is carried out by bringing the substrate in
contact with the chemical conversion treatment solution maintained
at a temperature of about 30.degree. C. for about 5 min-6 min.
6. The process as claimed in claim 1, wherein the refractory
compound is selected from one or more of the group consisting of
nitride of titanium, aluminum, chromium, zirconium, or cobalt;
carbonitride of titanium, aluminum, chromium, zirconium, or cobalt;
and oxynitride of titanium, aluminum, chromium, zirconium, or
cobalt.
7. The process as claimed in claim 6, wherein the ceramic coating
orderly includes a AlO layer adjacent to the molybdate conversion
film, a AlN layer on the AlO layer, and a AlON layer on the AlN
layer; the AlO layer is an aluminum-oxygen compound layer; the AlN
layer is an aluminum-nitrogen compound layer; the AlON layer is an
aluminum-oxygen-nitrogen compound layer.
8. The process as claimed in claim 6, wherein the ceramic coating
includes a AlON layer formed on the molybdate conversion film and a
CrON layer formed on the AlON layer; the AlON layer is an
aluminum-oxygen-nitrogen compound layer; the CrON layer is a
chromium-oxygen-nitrogen compound layer.
9. The process as claimed in claim 1, wherein the physical vapor
deposition uses a vacuum sputtering method or an arc ion plating
method.
10. The process as claimed in claim 1, further comprising etching
the substrate using an alkaline etchant containing about 40 g/L-70
g/L NaOH, about 10 g/L-20 g/L Na.sub.3PO.sub.4.12H.sub.2O, about 25
g/L-30 g/L Na.sub.2CO.sub.3, and about 40 g/L-50 g/L NaF, before
treating the substrate with the chemical conversion treatment
solution.
11. The process as claimed in claim 10, wherein the etching step is
carried out by immersing the substrate in the alkaline etchant,
which is maintained at a temperature of about 40.degree.
C.-50.degree. C., for about 3 s-5 s.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is related to co-pending U.S. patent application
Ser. Nos. 13/191,592, and 13/191,586, each entitled "PROCESS FOR
SURFACE TREATING ALUMINUM OR ALUMINUM ALLOY AND ARTICLE MADE WITH
SAME", each invented by Chang et al. These applications have the
same assignee as the present application. The above-identified
applications are incorporated herein by reference.
BACKGROUND
1. Technical Field
The disclosure generally relates to a process for surface treating
aluminum or aluminum alloy, and articles made of aluminum or
aluminum alloy treated by the process.
2. Description of Related Art
Aluminum and aluminum alloy are becoming widely used in
manufacturing components (such as housings) of electronic devices
and cars because of their many desirable properties such as light
weight and quick heat dissipation. However, aluminum or aluminum
alloy have relatively low erosion resistance and abrasion
resistance. One method for enhancing the erosion resistance of
aluminum or aluminum alloy is to form ceramic coatings on its
surface. However, magnesium alloy, typically casting magnesium
alloy usually has recesses on its surface. Portions of the ceramic
coatings corresponding to these recesses are usually thinner than
other portions, causing these portions to be easily corroded (also
known as pitting corrosion).
Therefore, there is room for improvement within the art.
BRIEF DESCRIPTION OF THE DRAWINGS
Many aspects of the embodiments can be better understood with
reference to the following drawings. The components in the drawings
are not necessarily drawn to scale, the emphasis instead being
placed upon clearly illustrating the principles of the exemplary
process for surface treating aluminum or aluminum alloy and
articles made with same. Moreover, in the drawings like reference
numerals designate corresponding parts throughout the several
views. Wherever possible, the same reference numbers are used
throughout the drawings to refer to the same or like elements of an
embodiment.
FIG. 1 is a cross-sectional view of an exemplary article treated by
the present process.
FIG. 2 is a cross-sectional view of another exemplary article
treated by the present process.
FIG. 3 is a block diagram of a process for the surface treatment of
aluminum or aluminum alloy according to an exemplary
embodiment.
FIG. 4 is a schematic view of a vacuum sputtering machine for
processing the exemplary article shown in FIG. 1.
DETAILED DESCRIPTION
Referring to FIG. 3, an exemplary process for the surface treatment
of aluminum or aluminum alloy may include steps S1 to S4.
In step S1, referring to FIG. 1, a substrate 11 is provided. The
substrate 11 is made of aluminum or aluminum alloy.
In step S2, the substrate 11 is pretreated. The pretreatment may
include the following steps.
The substrate 11 is chemically degreased with an aqueous solution,
to remove impurities such as grease or dirt from the substrate 11.
The aqueous solution contains about 25 g/L-30 g/L sodium carbonate
(Na.sub.2CO.sub.3), about 20 g/L-25 g/L trisodium phosphate
dodecahydrate (Na.sub.3PO.sub.4.12H.sub.2O), and an emulsifier. The
emulsifier may be a trade name emulsifier OP-10 (a condensation
product of alkylphenol and ethylene oxide) at a concentration of
about 1 g/L-3 g/L. The substrate 11 is immersed in the aqueous
solution, which is maintained at a temperature of about 60.degree.
C.-80.degree. C., for about 30 s-60 s. Then, the substrate 11 is
rinsed.
Then, the degreased substrate 11 is etched in an alkaline etchant,
to create a smooth surface and further remove any impurities. The
alkaline etchant is an aqueous solution containing about 40 g/L-70
g/L sodium hydroxide (NaOH), about 10 g/L-20 g/L
Na.sub.3PO.sub.4.12H.sub.2O, about 25 g/L-30 g/L Na.sub.2CO.sub.3,
and about 40 g/L-50 g/L sodium fluoride (NaF). The substrate 11 is
immersed in the alkaline etchant, which is maintained at a
temperature of about 40.degree. C.-50.degree. C., for about 3 s-5
s. During the etching, small sized protrusions on the substrate 11,
such as burrs, are dissolved.
In step S3, when the pretreatment is finished, a molybdate
conversion film 13 is formed on the substrate 11 by chemical
conversion treatment using a chemical conversion treatment solution
containing molybdate as the main film forming agent. The chemical
conversion treatment solution is an aqueous solution containing
about 8 g/L-15 g/L sodium molybdate (Na.sub.2MoO.sub.4), about 1
g/L-3 g/L sodium fluoride (NaF), and about 6 g/L-10 g/L potassium
permanganate (KMnO.sub.4). The pH value of the chemical conversion
treatment solution may be in a range between about 2 and 4.
The method of chemical conversion treatment is not particularly
limited, and can be performed under a common treatment condition by
bringing the chemical conversion treatment solution into contact
with the surface of the substrate 11. Examples of the method
include an immersing method, a dipping method, or a spraying
method. In this exemplary embodiment, the chemical conversion
treatment is carried out by immersing the substrate 11 in the
chemical conversion treatment solution maintained at a temperature
of about 25.degree. C.-40.degree. C. for about 4 min-7 min. In an
exemplary embodiment, the chemical conversion treatment solution is
an aqueous solution containing about 10 g/L Na.sub.2MoO.sub.4,
about 1 g/L NaF, and about 8 g/L KMnO.sub.4. The pH value of the
chemical conversion treatment solution is about 3. The substrate 11
is immersed in the chemical conversion treatment solution, which is
maintained at a temperature of about 30.degree. C., for about 5
min-6 min. During the chemical conversion treatment, the chemical
conversion treatment solution may be stirred. Thereby, a molybdate
conversion film 13 is formed on the substrate 11.
In step S4, a ceramic coating 15 is formed on the molybdate
conversion film 13 by physical vapor deposition (PVD), such as
vacuum sputtering or arc ion plating. The ceramic coating 15 may be
a single layer or multilayer refractory compound. The refractory
compound can be selected from one or more of the group consisting
of nitride of titanium, aluminum, chromium, zirconium, or cobalt;
carbonitride of titanium, aluminum, chromium, zirconium, or cobalt;
and oxynitride of titanium, aluminum, chromium, zirconium, or
cobalt.
In one exemplary embodiment, the ceramic coating 15 orderly
includes a AlO layer 151 coated on the molybdate conversion film
13, a AlN layer 152, and a AlON layer 153. The AlO layer 151 is an
aluminum-oxygen compound layer. The AlN layer 152 is an
aluminum-nitrogen compound layer. The AlON layer 153 is an
aluminum-oxygen-nitrogen compound layer.
Referring to FIG. 2, in another embodiment, the ceramic coating 15
includes an AlON layer 153 directly formed on the molybdate
conversion film 13 and a CrON layer 154 formed on the AlON layer
153. The CrON layer 154 is a chromium-oxygen-nitrogen compound
layer. An exemplary process for forming the AlON layer 153 and the
CrON layer 154 may be performed by the following steps.
The AlON layer 153 is directly formed on the molybdate conversion
film 13 by vacuum sputtering. The substrate 11 is held on a
rotating bracket 33 in a chamber 31 of a vacuum sputtering machine
30 as shown in FIG. 4. The chamber 31 is evacuated to maintain an
internal pressure of about 6.times.10.sup.-3 Pa to
8.times.10.sup.-3 Pa and the inside of the chamber 31 is heated to
a temperature of about 100.degree. C. to about 150.degree. C. The
speed of the rotating bracket 33 is about 0.5 revolutions per
minute (rpm) to about 1.0 rpm. Argon, oxygen, and nitrogen are
simultaneously fed into the chamber 31, with the argon acting as a
sputtering gas, and the oxygen and nitrogen acting as reaction
gases. The flux of argon is about 150 standard-state cubic
centimeters per minute (sccm) to about 300 sccm. The flux of oxygen
is about 30 sccm to 60 sccm, and the flux of nitrogen is about 15
sccm to about 40 sccm. A bias voltage of about -100 volts (V) to
about -300 V is applied to the substrate 11. Electric power of
about 8 kW to about 10 kW is applied to aluminum targets 35 fixed
in the chamber 31, depositing the AlON layer 153 on the molybdate
conversion film 13. Depositing the AlON layer 153 may take for
about 30 min-60 min. The power may be medium-frequency AC
power.
Subsequently, the CrON layer 154 is directly formed on the AlON
layer 153 also by vacuum sputtering. This step may be carried out
in the same vacuum sputtering machine 30. The aluminum targets 35
are switched off. The flux of oxygen is adjusted to about 40 sccm
to about 100 sccm, and the flux of nitrogen is adjusted to about 30
sccm to about 60 sccm. Electric power of about 8 kW to about 10 kW
is applied to chromium targets 37, depositing the CrON layer 154 on
the AlON layer 153. Depositing the CrON layer 154 may take for
about 0.5 hour to about 2 hours. Other parameters are the same as
during deposition of the AlON layer 153.
The molybdate conversion film 13 provides a smooth surface on the
substrate 11, and by such means the ceramic coating 15 formed on
molybdate conversion film 13 has a substantially even thickness,
reducing the susceptibility to pit corrosion. In addition, the
molybdate conversion film 13 firmly bonding with the substrate 11
has a good chemical stability and high density, having a good
erosion resistance. Having a high resistance to abrasion, the
ceramic coating 15 protects the molybdate conversion film 13 from
mechanical abrasion.
FIG. 1 shows a cross-section of an exemplary article 10 made of
aluminum or aluminum alloy and processed by the surface treatment
process as described above. The article 10 may be a housing for an
electronic device, such as a mobile phone. The article 10 includes
the substrate 11 made of aluminum or aluminum alloy, the molybdate
conversion film 13 formed on the substrate 11, and the ceramic
coating 15 formed on the molybdate conversion film 13 by PVD. The
molybdate conversion film 13 is formed by chemical conversion
treatment using a chemical conversion treatment solution containing
molybdate as the main film forming agent, as described above. The
molybdate conversion film 13 results from chemical reaction of the
chemical conversion treatment solution and the substrate 11. The
ceramic coating 15 may be a single layer or multilayer refractory
compound. The refractory compound can be selected from one or more
of the group consisting of nitride of titanium, aluminum, chromium,
zirconium, or cobalt; carbonitride of titanium, aluminum, chromium,
zirconium, or cobalt; and oxynitride of titanium, aluminum,
chromium, zirconium, or cobalt.
In one exemplary embodiment, the ceramic coating 15 orderly
includes a AlO layer 151 adjacent to the molybdate conversion film
13, a AlN layer 152 on the AlO layer 151, and a AlON layer 153 on
the AlN layer 152. The AlO layer 151 is an aluminum-oxygen compound
layer. The AlN layer 152 is an aluminum-nitrogen compound layer.
The AlON layer 153 is an aluminum-oxygen-nitrogen compound
layer.
Referring to FIG. 2, in another embodiment, the ceramic coating 15
includes a AlON layer 153 directly formed on the molybdate
conversion film 13 and a CrON layer 154 formed on the AlON layer
153. The CrON layer 154 is a chromium-oxygen-nitrogen compound
layer.
A neutral salt spray test was applied to samples created by the
present process. The test conditions included 5% NaCl (similar to
salt-fog chloride levels), that was neutral at 35.degree. C. to
simulate condensing gases with moisture and salt. The test was an
accelerated corrosion test for assessing coating performance.
Erosion began to be observed after about 72 hours, indicating that
the samples resulting from the present process have a good erosion
resistance.
It is to be understood, however, that even through numerous
characteristics and advantages of the exemplary disclosure have
been set forth in the foregoing description, together with details
of the system and functions of the disclosure, the disclosure is
illustrative only, and changes may be made in detail, especially in
matters of shape, size, and arrangement of parts within the
principles of the disclosure to the full extent indicated by the
broad general meaning of the terms in which the appended claims are
expressed.
* * * * *